Cancer is the second leading cause of death in developed countries. There is increasing evidence that most cancers are not due solely to genetics, but are rather a consequence of some environmental exposure. This is not to say that genetics are unimportant, because individuals vary in their susceptibility to chemical or other exposures. There are a variety of environmental exposures, and the most significant include radiation and carcinogenic chemicals. Everyone is exposed to radiation from natural and man-made sources. There are carcinogenic chemicals in our food, drinking water, and air. Exposure occurs at home, at the job and through leisure activities, and consequently each person is exposed to a mixture of carcinogenic exposures. There are also biological carcinogens, including certain viruses, bacteria and parasites. Much of our knowledge of causes of cancer come from animal, cellular and even human studies focused on one carcinogen at a time. In the real world, every human being is exposed to a mixture of carcinogenics. The goal of the Halifax Project is to assemble experts from around the world to focus attention on carcinogenesis of environmental mixtures. Eleven teams will be formed, each dealing with a specific form of cellular-level disruption. Participants will be placed into teams that will focus on specific hallmarks of cancer (angiogenesis; deregulated metabolism; evasion of anti-growth signaling; genetic instability; immune system evasion, replicative immortality; resistance to apoptosis; tissue invasion and metastasis; tumor microenvironment; tumor promoting inflammation), and a lead scientist will be identified for each team. Each team will identify environmental and/or occupational chemical exposures that are known to selectively disrupt the assigned mechanism, and consider the implications of using the hallmarks of cancer framework to assess the contributions of mixtures of disruptive environmental agents for risk assessment purposes. These reviews will be prepared in draft form in advance of the conference. The document will present the results and conclusions of the team on their assigned subject. Once finalized, these reviews will be published in a special issue of the journal, Carcinogenesis. An agreement to publish the conference proceedings has already been established. All members of the workgroup will be listed as authors. To date, 265 persons have expressed interest in attending and have indicated in which of the eleven workgroups they hope to participate. The applicants represent 33 countries, and most will be self-supported. Funds requested will be used for travel support for international experts, especially those from developing countries, as well as for women, racial/ethnic minorities, persons with disabilities, and other scientists or students who have been traditionally underrepresented in science.